1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device.
2. Description of the Related Art
In recent years, a proposal has been made of a nonvolatile semiconductor memory device having, between a control electrode and a charge storage layer, a high-dielectric-constant insulating film containing oxygen and a metal element in order to increase the capacitance between the control electrode and the charge storage layer and to improve charge retention characteristics (see, for example, Jpn. Pat. Appln. KOKAI Publication Nos. 5-129625 and 2003-68897).
However, if a silicon oxide film is deposited on the high-dielectric-constant insulating film, hydrogen or chlorine contained in film forming gas for the silicon oxide film may disadvantageously mix into the high-dielectric-constant insulating film, resulting in a reduction reaction or the like. This may cause oxygen vacancies in the high-dielectric-constant insulating film. Unfortunately, the oxygen vacancies may in turn reduce breakdown voltage, while increasing the amount of leak current and the amount of charge trap and charge detrap.
Thus, it has been difficult to form an excellent insulating film between the control electrode and the charge storage layer owing to problems such as oxygen vacancies attributed to hydrogen or chlorine.